1 Answer
1

Your folder structure looks fine, nothing to worry about there. However, you might not want to go any deeper that that, as research by moz.org says:

The quantity of subfolders in a URL appears to correlate to rankings. URLs with fewer trailing slashes perform better than those with more. Additionally, search engine representatives have recommended that excessive, subfolders in a URL string may be a signal that the page is very deep in a site’s structure and may be less valuable/worthwhile to crawl, index and rank.

Recommendation: Rewrite the URL to include no more than 3 subfolder
levels (4 trailing slashes following the domain name)

In your second question, if the content is only being served on a single URL, then there is no duplicate content to worry about, even if you are linking to the single page from multiple categories.